Battle of The Sexes: Do Gender and Sex influence Pain?

At PHRC, our therapists treat both men and women with pelvic pain conditions. Many of my patients are surprised to hear that men and women have almost the same pelvic floor muscles (with some minor variations).   If you were to ask me if I thought there was a big difference between treating women with pelvic pain vs men with pelvic pain, I would say no. However, most of us have heard at some point the idea that women have a higher pain tolerance than our male counterparts– “Women are tougher because they have to give birth” or “my husband gets the mildest cold and he has to stay home” are all too common phrases we hear. But in this day and age where we are moving towards men and women being seen as equals, it begs the question, is there truly a difference in the way and amount of pain we experience due to our different anatomies? And if there is, how is this affecting the care we are being provided? Andrea Nicol, MD, MSc, FASA from University of Kansas School of Medicine gave an excellent lecture at IPPS 2019 on the differences in pain perception & treatment between sexes. In this post, I’m going to share the information I learned from her lecture. 

What Is Pain?

In order to further explore the influencing factors of pain, it will be helpful to first define it. The International Association for the Study of Pain (IASP) defines pain as an “unpleasant sensory and emotional experience associated with actual or potential tissue damage.” Pain is a symptom of pathological process or injury. Often treating the injury or illness producing the symptoms results in reduction or elimination of pain. However, this does not always happen. Acute pain can become chronic pain which can be more difficult to treat. To treat chronic pain, looking at multiple dynamics including psychological factors, environmental factors, and past history is not only helpful, but necessary.¹  But is sex one of those crucial factors to take into account? 

Pain Perception

For the sake of this blog post, we’re going to separate sex from gender, and refer to male/men & female/women to chromosomal differences apparent at birth. Andrea Nicol discussed multiple ways in which men and women experience pain differently, the first is in the prevalence of pain.  Studies show that pain is more prevalent in females, and some studies show that women report greater subjective pain severity (i.e. women tend to report their pain as more severe than when males reported pain). 

 Why are women reporting more severe pain and reporting pain more often than men? Through studies that induced pain via quantitative sensory testing using various modalities, researchers found that healthy adult women have lower thresholds for pain and increased pain sensitivity than men. On the other hand, Men tend to display more intact inhibitory descending pain modulation which means their brains are better able to regulate their pain via dampening pain signals. 

Hormones can also affect how we experience pain. While estrogen and testosterone are present in both sexes, men tend to have more testosterone and women tend to have higher amounts of estrogen. Testosterone is mostly anti-nociceptive, meaning testosterone helps sensory neurons block painful stimuli. Alternatively, other sex hormones, estradiol & progesterone, were found to be pro- & anti-nociceptive. So the absence of testosterone’s anti-nociceptive effects combined with estrogen’s (at times) pro-nociceptive effects can result in higher pain sensitivity for women. Ultimately, lower androgen levels can be associated with increased pain. These effects are reinforced during periods of hormonal change such as menstruation or pregnancy. Hormonal changes were linked to women demonstrating increased pain sensitivity at the end of the luteal phase of their menstrual cycle and during follicular phase women were found to have higher pain thresholds. Increased pain thresholds were also found during pregnancy. 

Opioids

Opioid refers to “any substance that acts on an opioid receptor, including endogenous opioids present in the central nervous system.”²  The three major opioid receptors are Mu-opioid receptor (MOR), Delta-opioid receptor (DOR) and Kappa-opioid receptor (KOR). Mu-opioid receptors are associated with analgesic and addiction pathways in the brain. Women have higher mu-opioid receptor concentrations than men, which leads to an increased response to MU agonists (such as oxycodone). Essentially this means Mu-opioids have increased potency in females. Females also exhibited greater analgesia to Kappa-opioids. Meaning, If you were to give the same dosage of kappa-opioid to a male vs women, the women would demonstrate improved pain relief compared to males. However, the way our bodies are able to process opioids does not seem to be responsible for these difference in analgesic effects. More research is needed but it is clear there is an innate difference in how women & men respond to opioid agonists, whether Mu or Kappa opioids. 

Hormones also play a role in how we respond to opioids. Women in a high estradiol, low progesterone state tend to have decreased pain sensitivity and increased mu-opioid receptor binding, meaning during high estrogen states, women have better pain functioning. However, in low estradiol states women were found to have increased pain sensitivity and within the brain, decreased mu-opioid receptor binding & availability. This could mean that during peri-operative state—women may respond better to mu-opioid agonists nearing their period compared to low estrogen states.  

Psychosocial Factors Affecting Pain Coping Strategies 

Men and women tend to use different coping strategies for pain. Men often use behaviors to distract themselves and problem-focused tactics. Women tend to use social support, emotion-focused, attentional focused tactics, and positive self-statements to cope with pain. However, women have been shown to catastrophize more and have decreased self-efficacy than men. Catastrophizing is a coping style that consists of three components: magnification of pain, perceived helplessness, and rumination over pain.  Catastrophizing has been linked to poorer pain outcomes. Sociocultural beliefs and norms may affect pain perception as well. In many cultures, men are taught to be masculine, which often includes being “strong and tough”. These cultural norms affect how a patient will come to healthcare providers & discuss their pain. Women may feel more comfortable to talk about their pain and may feel more comfortable telling their provider a higher pain score. 

Pain Assessment & Treatment:

Studies have shown that patient AND provider characteristics influence how pain is perceived but also how it will be treated. Men and women are treated differently when it comes to pain. Often times women are told that the source of their pain is psychogenic or somatization, meaning “it’s in your head” leading to the undertreatment of pain in the absence of physical findings. Women are often prescribed sedatives over analgesics due to these biases. Female pain doctors are more likely to prescribe physical modalities or pharmacologic therapies first before recommending surgery and more invasive treatments, such as injections. Female practitioners are also more likely to recommend non-opioid analgesics compared to male practitioners. 

Dr. Nicol states that general patterns from research suggest that women are more often undertreated and frequently offered psychological treatment or drugs, (opioids and/or sedatives). Whereas men are more frequently offered physiotherapy, labs, radiologic studies, surgeries and analgesics.  It is important for patients and practitioners alike to be aware of these differences, as well as our own coping mechanisms and biases to help heal chronic pain in men and women. We thank Dr. Nicol for a fantastic lecture.

Sources: 

1. Rabow MW, Smith GT, Shah AC, Pantilat SZ. Pain. In: Feldman MD, Christensen JF, Satterfield JM, Laponis R. eds. Behavioral Medicine: A Guide for Clinical Practice, 5eNew York, NY: McGraw-Hill; . http://accessmedicine.mhmedical.com.ucsf.idm.oclc.org/content.aspx?bookid=2747&sectionid=230252149. Accessed November 05, 2019.
2. Henry SG. Opioids. In: Feldman MD, Christensen JF, Satterfield JM, Laponis R. eds.Behavioral Medicine: A Guide for Clinical Practice, 5e New York, NY: McGraw-Hill; . http://accessmedicine.mhmedical.com.ucsf.idm.oclc.org/content.aspx?bookid=2747&sectionid=230250416. Accessed November 10, 2019.